1. Field of the Invention
The present invention relates to computing systems providing normal security services and high security services with efficient resource utilization.
2. Description of the Related Art
In many consumer electronics such as mobile phones, PDAs, digital cameras, digital media and music players, handheld game consoles, and computer peripherals (such as hard drives and routers), two isolated operating environments are required for maintaining system security.
Normal security services, such as making a phone call and playing java games may operate in a normal security environment. However, when high security services such as online credit card payments are requested, the normal security environment may not satisfy security requirements of e-banking services. Instead, a high security environment isolated from the normal security environment is required to handle such high security services in order to prevent information theft.
Trustzone hardware architecture, developed by ARM, provides normal security services and high security services using a single physical processor core. Because only one processor core is required in the Trustzone hardware architecture, silicon size, manufacturing costs, and power consumption of the Trustzone hardware are considerably lower when compared with solutions using two dedicated processor cores. To isolate sensitive data from the malicious software disguised in a normal security environment, the single processor core of the Trustzone technique switches between a normal security state and a high security state to provide a normal security environment and a high security environment in a time-sliced fashion, and the hardware resources are design dedicated to the normal security environment or the high security environment.
However, the design of dedicated hardware resources results in low resource utilization. Resources such as file system, memory, registers, and engine dedicated to the high security environment are seldom used as the probability of switching to the high security state is typically low. To increase the utilization of these dedicated resources, the processor may frequently switch between the two security states. For example, services involve sensitive data or require dedicated hardware resources in a high security environment will be performed in the high security environment. Frequent switching of security states occurs. Latency and power consumption caused by switching of security environments are considerable.
Thus, a way to simultaneously reduce switching of security environments and increase utilization of hardware resources is called for.